Will a permanent 3.3v connection to ADC drain the battery

FFMan · Post by **FFMan** » 24 November 2020, 12:50 PM

Like the title says, can i connect my regulated lipo output to an adc pin and have it not drain the battery at all when the ZX is not powered up.

At the moment I have the adc pin connected to the input to the regulator which is always in safe range, however, i now want the option to power it from 12v, which the regulator (Anyvolt) will be fine with, but this would over volts the adc pin as things stand.

thanks

FFMan · Post by **FFMan** » 24 November 2020, 13:05 PM

Actually, i don't this will work as the voltage divider will create a drain to ground anyway.

Post by **dkinzer** » 24 November 2020, 13:40 PM

Even though you said that this won't work for you I thought that I'd answer it anyway for the record. If you look at the datasheet where it depicts the protection diodes, you'll see that there is a clamping diode with its anode connected to the pin and its cathode connected to Vcc. Because of this, any signal connected to an I/O pin can power the chip through the clamping diode when Vcc is lower than the signal voltage less the diode drop.

FFMan · Post by **FFMan** » 24 November 2020, 14:09 PM

ah yes - i rather suspected that might happen also.

I think i need a DPDT switch, it's just fitting it in but I think i can do it.

thanks Don